Why do you want to do that?  It is unusual to want a CMDB to be so out of date.

You cannot configure when Discovery does do CMDB sync activity, but you can specify a blackout window that specifies when it must not. If you look at the "Monthly by week of month" option in the blackout window, you can black out all but two days each month, which is nearly the same as what you want. Or if weekly is not too "fast", you can allow it only on one day per week with the "Weekly by days of week" option. This assumes that the CMDB would be able to handle the volume of change within its permitted window, otherwise it would fall even more behind than you want.

Of course the alternative would be to only schedule Discovery to scan every two weeks, then the continuous sync would be that infrequent as well.

Yes, they are queued and automatically synchronized when the blackout window is over.